The Local Group environment at 1-10 Mpc expands linearly and smoothly,
as if ruled by uniform matter, while
observations show on the same scales the very lumpy local galaxy universe.
This enigma in cosmology
has also been demonstrated by high-resolution N-body CDM simulations.
We suggest that the homogeneous dark energy component,
revealed by SNIa observations, may resolve the problem
of the local cold Hubble flow
within the highly non-uniform environment.
Linear density perturbations on a homogeneous background
with the equation of state
are decaying for .
Exact non-linear Einstein's equations for a spherically
symmetric matter concentration,
show that
there is a zero-mass surface where the positive mass of the local cloud
is compensated by the negative dark energy mass, and beyond
this surface
dark energy dominates dynamically.
In such regions the velocity dispersion is adiabatically cooling, and
this may explain why the Hubble law starts
on the outskirts of the Local Group, with the same H0 as
globally and with a remarkably small velocity dispersion.

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